Creating the Perfect Fit: New Car Seat Design

Trying To Please All of the People, All of the Time

Oh, My Aching Back! Lumbar Support and Head Restraints

Because your back plays such an important part in how you feel no matter where you are, making a seat comfortable in terms of back support remains the highest aim of vehicle seat designers.

But it's getting more difficult for car seat designers to ease everyone's back in the cockpit. Larger bodies are more difficult to fit properly. And as we age, our spines curve more, meaning that auto companies have to pay special attention these days to the aging baby boomer demographic.

"There are seven different theories about what causes lower back pain," said Terry O'Bannon, a principal designer for seat supplier Lear. "But the main thing we focus on in seat design is reducing postural muscle activation. If you're having to hold yourself up when you sit down, then the muscles are continually having to work. And you get fatigue and joint pain."

Paying Attention to Lumbar Support

Lumbar support is crucial to this effort. Overall, the auto industry is acknowledging its importance by generally, and gradually, increasing the frequency of lumbar-support systems in seats and their provision as standard equipment, Edmunds.com research shows.

For 2007 model-year vehicles, 78 percent offer driver or driver/passenger lumbar support as standard or optional, a significant rise from 71 percent of models that did so for the 2004 model year, according to Edmunds.com research.

This model year, 29 percent of models offer driver-only lumbar support on a standard basis, the research found, up from a comparable figure of 26 percent for the 2004 model year. Meanwhile, 45 percent of models for the 2007 model year offer driver/passenger lumbar support as standard or optional, up from 43 percent in 2004.

Yet the consensus of the seat-design community is that, in general, import brands are making lumbar supports more widespread, or more often standard, while the domestic Big Three are more likely to be "decontenting" the vehicle of lumbar supports in cost-cutting moves.

"We see our Asian customers generally increasing the use," said Barry Jones, president of Leggett & Platt Automotive Group North America, a Windsor, Ontario-based operation that relies on lumbar supports for more than half of its revenues. "And we see our North American customers maintaining where they're at or slightly decreasing."

Sometimes, carmakers chip away at costs by removing lumbar supports from the front passenger seat while leaving them on the driver side. "From driver to passenger side, it's a constant battle on the front row," said Mike Grajek, General Motors' lead engineer for human vehicle integration. For the sake of costs and profit margins, automakers neither want to "give away" lumbar supports compared with competitors, nor make them glaringly absent.

Overall, car seat designers acknowledge the growing importance of lumbar support to consumers. "When you have lumbar support and the following [model] year that support is taken out for some reason, the seat sees a dramatic decrease in comfort," said Don Bernhardt, Lear's vice president of seat engineering. And consumers know it right away."

How Lumbar Supports Work

Usually, lumbar-support systems in seats are built mechanically around a metal plate that has a surface of as much as a square foot, sometimes resembles a rib cage and weighs a pound or two. Other systems are pneumatic, meaning a bag is inflated. Typically, lumbar supports can be manually or electronically activated to extend into the seat cover and gently push the support into the lumbar areas of the lower back.

A number of variables can determine how effective a lumbar-support system is in practice, including the materials used, how well the system is integrated with the rest of the seat and whether adjustments move only in and out or also up and down.

"Consumers want the flexibility of adjustable lumbars," said Steve Nunez, supervisor of seat-comfort attribute development for Ford. "There are so many different sizes and shapes of customers that we can't find the single optimal spot for lumbar support. And people are aging and have different back ailments and conditions. Adjustable lumbars allow us to find the sweet spot to offer them the most relief and give them the best posture."

Head Restraint Rule Complicating Seatbacks

The latest challenge facing seat designers is a new federal whiplash-prevention standard; it requires both front and rear headrests to be higher and closer to the backs of people's heads, similar to those mandated by the European Union. So beginning in September 2009, U.S. automakers will have to phase in head restraints that lock once they're in position and aren't removable — including those on rear seats that tilt or fold for loading purposes. Vehicle seat designers must choose between placing "passive" restraints closer to occupants' heads or designing "active" mechanisms that instantaneously move restraints forward to support the head if a vehicle crashes. (For details, see "Pain In the Neck.")

But consumers have demonstrated that they will tend to resist, by whatever means necessary, having restraints moved closer to their heads. "The occupant gets a pressure feeling," said Michael Sweers, general manager of engineering design for Toyota Motor Engineering & Manufacturing North America. "It doesn't affect their comfort, but it's like being in a tight space and you feel like it's touching you."

Many consumers, research predicts, will simply recline their seatbacks more. This maneuver, of course, tends to offset the back and lumbar support that has been built into these seats and makes it more difficult for designers to make the seats comfortable and supportive of the back. Automakers and seat suppliers are responding in part by adding more foam in upper seatbacks so they are more upright and the neck-to-torso angle is more comfortable, said Ford's Nunez.

Still, certain types of drivers probably are predicted to resist the most. Boomers are less accepting of the closer head restraints than younger drivers, the companies say. Women, out of concern for their hairstyles, are more disconcerted by closer restraints than men are. The shortest drivers will have the biggest problems because they must keep the seat high and the backrest extremely vertical.

And in the American West, automakers expect complaints from drivers who prefer wearing cowboy hats to putting up with a head restraint: Now, they'll have to take off their 10-gallons before they sit down.

Add the new head-restraint standard to the list of reasons why designing seatbacks — and cushions, and bolsters — is still as much an art as a science. And it will be as long as drivers are, well, human.

Comments

Great article and only one point missing. There is only one tool available for seat design that comprehends the complete list of issues you described from body size to safety, posture for the back to comfort. This tool is not in use. Research began in 1991 at Michigan State University and the math tool was developed and validated by ERL LLC from 2000-2008. It is based on a math model of the seat and digital human bodies that represent the small woman to the large man sitting in erect, neutral and slumped back postures. Currently, there is no seat design at the OEM where the interior architecture is established for head restraint, H-point tests, etc. and seat travel is defined by statistics. Only with a math tool like ERL, seat design can become part of advanced engineering at the OEM to create Design Position and seat specifications that meet the needs for healthy and comfortable seating for all drivers.

† Edmunds.com received the highest numerical score in the proprietary J.D. Power 2014 Third-Party Automotive Website Evaluation Study℠. Results based on responses from 3,381 responses, measuring 14 companies and measures third-party automotive website usefulness among new and used vehicle shoppers. Proprietary study results are based on experiences and perceptions of owners surveyed from January 2014. Your experiences may vary. Visit jdpower.com.